Anisotropic thermal expansion of potassium dinitramide: a variable-temperature crystallographic study

The structure of potassium dinitramide (KDN) has been refined from X-ray diffraction data in the temperature range 85–298 K. The thermal expansion is significantly anisotropic and correlated to the atomic displacement parameters. A rigid-body analysis of the dinitramide anion was carried out. The variation of thermal motion with temperature indicates anharmonicity in the mean field potential.

Qu­antifying distortion from ideal closest-packing in a crystal structure with analysis and application

An isotropic distortion parameter has been defined that quantifies the departure of the anion skeleton of a crystal from ideal closest-packing. Analysis of the variation in this parameter for a variety of rock-forming minerals at various temperatures and pressures elucidates the important role of anion–anion interactions during expansion and compression.

Synchrotron X-ray analysis of the electron density in CoF₂ and ZnF₂

Structural, multipole and orbital analyses of the electron density in the rutile-type compounds CoF₂ and ZnF₂ have been performed using synchrotron X-ray data.

Synchrotron X-ray study of Er₃Al₅O₁₂ and Yb₃Al₅O₁₂ garnets

Structure factors for the Er₃Al₅O₁₂ and Yb₃Al₅O₁₂ garnets were measured with synchrotron X-radiation at room temperature. Approximate difference electron density symmetry around the rare-earth atoms was found to reflect that of the cation geometry, emphasizing the importance of second nearest-neighbor interactions.

Characterization of the room-temperature phase of Tl₂MoO₄: crystal structure, symmetry mode analysis and second-harmonic generation measurements

The structure of Tl₂MoO₄ at 293 K has been refined and compared to the structure at 350 K. Second-harmonic generation measurements and symmetry mode analysis have been performed.

Reversible phase transitions in Na₂S under pressure: a comparison with the cation array in Na₂SO₄

The antifluorite Na₂S, disodium sulfide, undergoes, under pressure, two phase transitions adopting the anticotunnite and the Ni₂In-type structures. The latter is just the structure which presents the cation array in the high-temperature phases of Na₂SO₄. An equivalence between oxidation and pressure is established, in the sense that both stabilize the Ni₂In-type structure as if the Na and S atoms were recognized in spite of being embedded in an oxygen matrix.

A novel perovskite-like Ta-bronze KTa_1+zO₃: preparation, stoichiometry, conductivity and crystal structure studies

KTaO₃, an oxide bronze, has been synthesized by electrolytic crystallization. The high-resolution anharmonic crystal structure refinement reveals the presence of Ta₂ dumb-bells in the KTaO₃ matrix, which explain the semiconductor property.

Systematic ab initio study of the compressibility of silicate garnets

The structures of a number of cubic silicate garnets at ambient pressure and under compression have been investigated using first-principles pseudopotential calculations.

Structure determination of two intercalated compounds VOPO₄·(CH₂)₄O and VOPO₄·OH—(CH₂)₂—O—(CH₂)₂—OH; synchrotron powder diffraction and molecular modelling

The structure of two intercalated compounds VOPO₄–thf and VOPO₄–DEG were determined by a combination of high-resolution synchrotron powder diffraction and molecular modelling. Both intercalates exhibit the same type of orientational disorder as observed in VOPO₄ intercalated with water.

Ab initio structure determination of monoclinic 2,2-di­hydroxymethylbutanoic acid from synchrotron radiation powder diffraction data: combined use of direct methods and the Monte Carlo method

The crystal structure of the monoclinic form of 2,2-dihydroxymethylbutanoic acid (C₆H₁₂O₄) has been determined ab initio using synchrotron radiation powder diffraction data. A partial direct method soluition was completed using Monte Carlo techniques.

Patterns of soft C—H⋯O hydrogen bonding in di­aryl sulfones

Soft C—H⋯O hydrogen bonds link molecules of substituted diaryl sulfones into aggregates which can be zero-, one-, two- or three-dimensional.

Salts of 3,5-di­nitro­benzoic acid with organic di­amines: hydrogen-bonded supramolecular structures in one, two and three dimensions

3,5-Dinitrobenzoic acid forms salt-type 2:1 adducts with a range of organic diamines. The ions are linked into three-component aggregates by N—H⋯O hydrogen bonds, and these aggregates can be further linked by combinations of N—H⋯O and C—H⋯O hydrogen bonds into continuous arrays which may be one-, two- or three-dimensional.

Structures of furanosides: geometrical analysis of low-temperature X-ray and neutron crystal structures of five crystalline methyl pento­furanosides

Accurate X-ray and neutron structures of the five crystalline methyl pentofuranosides allow for detailed investigation of furanoside ring geometry.